1. Field
Embodiments of the present invention relate to a clothes dryer having a heat pump.
2. Description of the Related Art
For example, in a rotary drum type clothes dryer, a filter is installed in an exhaust path for wet air discharged from clothes. In addition, a detection unit is configured to detect clogging of the filter and emit an alarm or the like when clogging is detected. For example, a differential pressure sensor configured to detect a pressure difference upstream and downstream from a heat exchanger is known to be used as the detection unit. That is, it is determined that filter clogging is generated when the pressure difference is a predetermined level or less according to reduction in flow rate of the passing air (for example, see Patent Literature 1).
In addition, in general, as a sensor configured to detect a flow velocity or a flow direction of fluid (a gas), there is a sensor including a center main column installed at a center of a base, two temperature compensation thermistors installed in parallel on an upper end surface of the center main column, side main columns installed with the center main column interposed therebetween and having a height smaller than that of the center main column, and flow velocity sensors mounted on upper end surfaces of each of the side main columns to react with heat taken by the fluid to detect a flow velocity (for example, see Patent Literature 2).
In addition, among sensors (anemometers) configured to detect a flow velocity of such a gas, there is a sensor having a sensor unit configured to measure a wind velocity and surrounded by a cylindrical rectification member.
For example, in Patent Literature 3, an airflow meter installed at a suction path of an engine is disclosed, and the airflow meter is constituted by a heat generating resistor disposed at a cylindrical subsidiary passage or in the inside thereof, a thermosensitive resistor for temperature compensation, and so on.
However, when the differential pressure sensor is used as described above, a pipe communicating between an air passage and differential pressure sensor should be provided. For this reason, a structure thereof may be complicated and manufacturing cost may be increased.
In addition, the inventor(s) has attempted to apply a sensor configured to react with heat taken by fluid to detect a flow velocity as disclosed in Patent Literature 2 to a clothes dryer for filter clogging detection. However, the filter clogging cannot be precisely detected due to many detection errors.
In addition, a lint filter should be detached and attached when cleaned. When the lint filter is imperfectly mounted, a gap may be generated and lint may intrude into the exhaust path. Accordingly, when the above-mentioned anemometer is used in the clothes dryer, the lint may be caught by the rectification member to cause unstable measurement. The lint caught by the rectification member should be manually removed. Accordingly, on all such occasions, the dryer should be disassembled and the anemometer should be taken out, thus requiring a complex operation.
In addition, as a conventional heat pump type clothes dryer, there is provided a clothes dryer shown in FIG. 36. In the clothes dryer, air suctioned into the suction flow path to be suctioned into the drum configured to accommodate clothes is heated in a condenser (a radiator) and an auxiliary heater. Further, there is an exhaust-type heat pump dryer configured to evaporate moisture of clothes in a drum, collect heat from air having a high temperature and high humidity exiting the drum by an evaporator (a thermal absorber) installed at an exhaust flow path, and exhaust the air.
In order to reduce a drying time using the exhaust-type heat pump dryer, a heating capacity of the suction flow path should be increased, and a heat collecting amount of a thermal absorber should be increased for the sake of thermal efficiency.
However, when a large capacity compressor is applied to the exhaust-type heat pump dryer according to a standard condition, a refrigerant temperature or a refrigerant pressure in a heat pump circuit is increased to heat the suctioned refrigerant to a high temperature and thus increase a compressor temperature when operated under an overload condition such as when an external air temperature is high or a load is large. Accordingly, the compressor temperature may deviate from an allowable use range and the compressor may overheat or stop. In order to prevent these problems, use of the large capacity compressor should be avoided and a compressor capacity should be reduced. However, in this case, a capacity of the heat pump is decreased and a drying time upon normal operation is also increased.
While not provided in the exhaust-type heat pump dryer, as a countermeasure of the high temperature and high pressure of the refrigerant in the circulation type heat pump dryer, as disclosed in Patent Literature 4, there is a method of decreasing a refrigerant temperature of a heat pump circuit by providing an auxiliary condenser in addition to a heat exchange stove in a circulation type heat pump circuit and radiating heat from the auxiliary condenser to the outside of the heat exchange stove. However, in order to efficiently radiate the heat to the outside of the heat exchange stove, an exclusive blower configured to blow air should be installed at the auxiliary condenser, which may cause an increase in size or cost of an apparatus.
In addition, while a method of cooling the auxiliary condenser using drained water may be employed to improve radiation efficiency, when the water cooling is performed, the heated drained water is evaporated, causing dew condensation in the housing or an increase in temperature and humidity therearound.
FIG. 37 shows a configuration in which an auxiliary condenser is provided in addition to the heat exchange stove of the conventional exhaust-type heat pump dryer. However, in such a configuration, similarly, in addition to the heat exchange stove, an exclusive blower configured to blow air to the auxiliary condenser is required to efficiently radiate heat, which may cause an increase in size or cost of the apparatus. In addition, when the auxiliary condenser is cooled using water such as the drained water or the like, the temperature of the drained water that absorbs heat may be increased and cause dew condensation in the housing or an increase in temperature and humidity.
In addition, in the above-mentioned exhaust-type heat pump clothes dryer, when the external air temperature is low, the refrigerant temperature and the refrigerant pressure in the heat pump circuit are decreased to decrease the temperature of the refrigerant introduced into evaporator, generating frost on the evaporator. When the frost is generated, the evaporator may become clogged.
In order to solve these problems, there is provided a method by which a compressor capacity can be reduced and a decrease in temperature of the refrigerant to a temperature below zero can be prevented even when low temperatures are used. However, when the compressor capacity is reduced, a drying capacity under the standard condition (the normal temperature) may be decreased.
In addition, as another method, there is a method of increasing a capacity of an evaporator or a method of employing a variable displacement compressor such as an inverter or the like. However, when generation of the frost is prevented by only an increase in evaporator capacity or the variable displacement compressor is employed, cost may be increased.
In addition, while not provided in the exhaust-type heat pump clothes dryer, as a countermeasure of the frost generated on the thermal absorber in the circulation type heat pump clothes dryer, as disclosed in Patent Literature 5, a high pressure pipe configured to heat the thermal absorber through a portion of the thermal absorber upstream from a decompression unit using a high pressure refrigerant supplied from a radiator disposed upstream from the refrigerant circuit is provided.
However, in the method disclosed in Patent Literature 5, the thermal absorber itself is heated but the temperature of the refrigerant introduced into the thermal absorber is not increased. Accordingly, when the external air temperature is low, the problem such as the decrease in temperature of the refrigerant introduced into the thermal absorber cannot be solved.